A series of 120 patients with recurrent urinary tract infection (UTI), all in acute recurrence at the start of the trial, were treated for 3 months under double-blind conditions with 1 capsule daily of either the immunobiotherapeutic product Uro-Vaxom (UV) or a placebo. They were then observed for 3 months without treatment. During the 6 months of the trial a significant decrease was noted in the UV group compared with the placebo group with respect to the number of recurrences of UTI, total consumption of antibiotics and chemotherapeutic agents, bacteriuria and dysuria. By the sixth month the UV patients were receiving no antibiotics. The final assessment was that UV was significantly more effective than the placebo. UV was well tolerated, with possible mild side effects in only 4 patients. During a further observation period of 5 months, patients who had received UV during the first period had fewer recurrences of UTI than those who had received placebo, confirming the long-term protective action of UV.